This invention relates to underground mining. More particularly this invention relates to a hydraulic underground mining system in which mining at significant depths is accomplished by means such that a hydraulic mining fluid is introduced as a jet within a subterranean ore body to form a slurry in which form the ore is removed and brought to the surface.
Subterranean mining of ore bodies by hydraulic mining through well bores has been known, as for example, as set forth in the patent to Aston U.S. Pat. No. 2,518,591. Such mining takes place by slurrification of material in a subterranean mineral deposit and removal of the slurrified material. In the past, jet pumps have been used to lift the slurry out of the mining area. However, the use of jet pumps limits the lift height to .[.valves.]. .Iadd.values .Iaddend.which are inadequate for many ore bodies. In addition, jet pumps tend to require large quantities of motive water which results in a very dilute slurry having too low a solids content. This results in consumption of excessive energy and water.
Pressure lift systems have also been proposed, as for example, in the U.S. Pat. No. 3,439,953 to Pfefferle. In such systems, a well bore casing is sealed to the surrounding ground and sufficient pressure is then applied in the subterranean deposit, i.e., internally of the ore body to expel slurrified contents through a conduit to the surface. Such a pressure system is relatively expensive to operate due to weight and power required to make up for seepage loss caused by the porosity of the region surrounding the mined area and also due to the difficulty of maintaining a casing seal under pressures adequate to drive the slurrified material to the surface. Such systems are also subject to casing failure or to failure of the seal. Where the casing or seal has failed, mining through that bore usually becomes impractical and if the overburden subsides upon loss of pressure the entire rig may be unrecoverable. In addition, most prior art systems have required large well bores, often in excess of 2 feet. The cost of drilling large well bores is often too high to permit economic recovery of even shallow ore deposits. There is therefore, a need for a new and improved subterranean mining method and apparatus.